In oil and gas drilling, a wellhead typically refers to a series of spools, valves and adapters that are located at the surface of a wellbore and that provide pressure control for the wellbore. During production, a wellhead typically includes a casing head, a tubing head that is landed on the casing head, and a series of valves, spools, pressure gauges and the like (a “Christmas tree”) mounted on top of the tubing head and used to control the flow of formation fluids out of the wellbore. Often, during drilling, in lieu of the Christmas tree a blowout preventer may be mounted on the tubing head. The blowout preventer is used to safely deal with extremes in pressure that may be unexpectedly encountered during drilling.
Because of the nature of the equipment used and the dangers associated with oil and gas drilling, installing and changing the configuration of wellheads is a time consuming, potentially dangerous, and costly process. Accordingly, research and development continues into improving the deployment and design of wellheads.